In particle beam devices, an object may be precisely positioned in order to be examined. After all, this is the way to select interesting areas of an object and to examine them using a particle beam. The use of a holder in the form of an object stage which is adjustable in three directions arranged perpendicular to each other and on which an object to be examined is situated, has long been known for positioning an object. The object stage may also be rotated around a first axis and/or tilted around a second axis.
To roughly position the object stage, and thus the object, with regard to a particle beam, a positioning auxiliary device for a particle-optical scanning microscope is known from DE 10 2006 047 729 A1, which is incorporated herein by reference, the particle-optical scanning microscope being provided with an objective which defines a particle-optical beam axis and also with an object stage. The known positioning auxiliary device includes a light source in the form of an illumination device for generating a light beam at a first angle relative to the particle-optical beam axis. The light beam intersects the particle-optical beam axis at a predefined position. The known positioning auxiliary device is also provided with a detector in the form of a camera, which is sensitive to the wavelength of the light beam and which is used to take a photo of an object situated on the object stage at a second angle relative to the particle-optical beam axis. In addition, the known positioning auxiliary device includes a display and a control device for generating a photo taken by the camera on the display, together with a mark which indicates the position of the particle-optical beam axis in the photo. Using the known positioning auxiliary device, it is possible to roughly position the object stage with regard to a particle beam. The object stage is adjustable in a plane which is perpendicular to the particle beam incident upon the object. However, it is possible to position the object stage with sufficient accuracy only if the distance of the plane of the object situated on the object stage is equal to the working distance predefined by the objective. Positioning at a different working distance is not provided.
Reference is also made to U.S. Pat. No. 7,205,542 B1 that discloses a scanning electron microscope with curved axes and which is incorporated herein by reference.
Accordingly, it would be desirable to specify a positioning device and a particle beam apparatus including a positioning device which ensure reliable and sufficient positioning of a holder for holding an object or for positioning the object at any working distance.